Method of producing hard compositions of matter



Sept. 21', E931.. P; M.. McKENNA METHOD @TF FRLQDUC'ING HABD @OMPOSI'B'IQJN'S QF' MLK-ITER @riginal Filled, Sep-t.. 6 1935 glu/venten Patented Sept. 21, 1.937

UNITED STATES PATENT orticaV METHOD F PRODUCING HARD COMPOSI- TIONS 0F MATTER Philip M. McKenna, Latrobe, Pa.

15 claims. (ci, 7;-137) `My invention relates to the method of producing new hard compositions of matter. This application is a division of my pending application for Letters Patent for Hard compositions of matter and the method of producing the same, Serial Number 39,505, led September 6, 1935. It has to do, more particularly, with the method of producing certain novel compositions of matter, notable for their combined strength and hardness,A so that they are particularly useful in the construction of tools, dies and other articles of wear-resisting or corrosion-resisting nature, as well as articles which are required to resist deformation or destruction at high temperatures and pressures. In particular, my invention relates to the production of new hard compositions of matter, which are particularly useful as the hard bits or tips `including the cutting edges of tools intended for cutting hard materials. These compositions are also particularly adapted to use as wire-drawing dies. L The principal object of my invention is to provide a new method for producing hard compusitions of matter, by which compositions may be produced having greater combined strength, hardness and resistance to deformation, especially at high temperatures, than has been possible heretofore.

A further objecty of my invention is to Aprovide a new method of making hard compositions of matter, by which greater combined strength and hardness is obtained, due to the fact that I use as an ingredient a carbide of a metal of the group including tantalum and columbium, hav- I ing in solid solution therein'one or more of the carbides of the metals 'of the 'groups including tantalum, columbium, titanium and zirconium.

A further object of my invention is a new method of producing hard compositions of matter, of great combined strength and hardness, which is characterized by the use as an ingredient of a carbide of the metals of the group including tantalum and columbium, with or without minor constituents consisting of a carbide or carbides of the metals of the group including tantalum, columbium, titanium and zirconium, which are of differing or diverse grain size.

A further object of my invention is to provide a new method of making hard compositions of matter, of the type including a carbide of one or more of the metals of the group including tantalum and columbium, which is characterized by a special treatmentof the non-oxidizing liquid bath, in which the ingredients are ground to the size desired for use, by means of which oxidation of the grains of material is prevented, with the result that a superior product is obtained.

A further objec't of my invention is to provide a new method of making hard compositions of matter, of the type including a carbide of tantaluni or columbium as an ingredient, which is characterized by heating the ingredients to form hard compositions under a degree of vacuum much greater than has heretofore been used, with the result that a considerably better product is obtained.

A further object of my invention is to provide a novel methodof producing hard compositions of matter, of the type including a carbide of a 15 metal of the group including tantalum and columbium, and also a carbide of a metal of the group including titanium and zirconium, by which the titanium carbide or zirconium carbide may be introduced into the composition without oxidation and the resultant loss of strength. l

'A further object of my invention is to provide a new method of making hard compositions of matter, of the type including a carbide of a metal of the group including tantalum and columbium, in which a larger proportion of freshly fractured surface of the grains of said carbide is provided, whereby a more effective union of the grains of carbide through the medium of metallic tungsten, or molybdenum, and nickel, or other metals of the iron group, is effected, with the result thata hard composition is produced having greater combined strength, hardness and resistance to deformation, than has been possible heretofore.

A further object of my invention is to provide a method of making hard compositions of matter, of the type including a carbide of a metal of the group including tantalum and columbium, together with a metal or metals having the function of uniting the grains of carbide into a cohesive mass, which enables one to obtain a uniform product with certainty.,

Further objects, and objects relating to details and economies of production and operation, will definitely appear from the detailed description to follow. In one instance, I accomplish the objects of my invention` by the devices and means set forth in the following description. My invention is clearly defined and pointed out in the appended claims. The annexed drawing, forming a part of this specication, illustrates diagrammatically a form of apparatus which I have found useful in carrying out one step of my new process.

Hard compositions of matter have been known, heretofore, which consisted of an amorphous material, called tantalum carbide, together with certain proportions of a metal or metals of the group including tungsten and molybdenum, and a metal or metals of the group including iron, cobalt and nickel. The best of these hard compositions of matter was composed as follows: Amorphous tantalum carbide, 78 per cent, nickel, 10.2 per cent, tungsten 11.8 per cent. This material was made by comminuting the amorphous tantalum carbide and metallic tungsten in a ball mill, using nickel balls, in a bath of naphtha, until the mixture contained the tanta; lum carbide, tungsten and nickel in the desired degree of iineness and in the required proportions above given. The naphtha was then removed entirely by heating in a partial, vacuum at a red heat.. A piece was then formed from this dried powder of the desired shape and that piece heated in an electric furnace, under a partial vacuum, corresponding approximately to a pressure of from 70 to 80 microns of mercury, for forty minutes. As the result of this treatment, a hard composition of matter was formed having a Rockwell A hardness of 86.5. 'I'he strength of the piece thus formed is indicated by the fact that the piece, having a thickness of .200 inch and a width of .375 inch, resting on supports H of an inch apart, when pressed in the middle with.

a one centimeter Brinell ball, broke under a load of 1980 kilograms.

Another exampleof similar hard compositions of matter, heretofore known, is one which comprised 80 per cent amorphous tantalum carbide, 8 per cent nickel and 12 per cent tungsten. This composition had a Rockwell A hardness of 87.75 and broke, under the same conditions as speciiied above, at a load of 1500 kilograms. These two hard compositions of matter, just described, represent what I believe to be the most desirable hard compositions of this type heretofore made, known or used. l

These compositions were made from a material which was called tantalum carbide, but in which the carbon was not present in exact monatomic ratio to the tantalum. 'I'his material was amorphous in character, in that it did not present crystalline form to the unaided human eye. For the purposes of this specification I define macro-crystalline as having particles which average greater than .01 millimeter in largest cross section dimension and amorphous as having particles which average less than .01 millimeter in largest cross section dimension. I understand that there is another sense, in which all solid bodies may be described as crystalline, and may be shown to have ordered atomic arrangement by X-ray methods, or to have crystalline form which may be seen under the microscope, but I do not use the term in this sense, in this specification.

It will be observed that. in the two composi' ltions above-mentioned, the nickel and tungsten together constitute 22 per cent and 20 per cent, respectively, of the composition, and that the tungsten constitutes 53.6 per cent and 60 per cent,

respectively, of the ingredients of the composition other than the tantalum carbide. I had believed it desirable, if possible, to increase the proportion of tungsten in the noncarbide ingredients of the composition, but I had found that this was not feasible, heretofore, because a further increase in the proportion of tungsten resulted in a decrease in the strength of the composition,

76 which was undesirable-,las the piece would break could not be obtained, heretofore, without an accompanying decrease in the strength-of the composition.

Hard compositions of matter have been proposed, heretofore, including columbium carbide, of the amorphous type in which the carbon is not present in true monatomic ratio to the columbium, together with certain proportions of tungsten and cobalt, but such hard compositions were lacking'in practical value, because of the weakness of the material.

It has also been proposed, heretofore, to make hard compositions of matter from a mixture of amorphous tantalum carbide and amorphous columbium carbide, the particles of which were united into a cohesive mass by a mixtureof metallic iron and molybdenum. Although such compositions were hard, they were lacking in strength as they would break under a load which the desired degree of neness and to incorporate in the mixture the desired proportions of a metal or metals of the group including tungsten and molybdenum, and ofv a metal or metals of the iron group. The powdered mixture thus formed after drying off some of the naphtha is pressed to the shape of the piece to be made, the linear dimensions, however, being from 15 to 25 per cent greater than those of the ultimate piece, depending upon the shrinkage which takes place in the process, and the piece thus shaped is heated, under a partial vacuum, in an electric furnace, for about forty minutes, at a temperature of about 1430 C. The heating should require about two hours in all, one hour and twenty minutes being consumed in gradually raising the furnace to the ultimate temperature and removing the` gas and vapors, and the furnace being maintained atv the ultimate temperature for about forty minutes. As a result of this treatment, the shaped piece shrinks into a cohesive bit of like shape, but smaller dimensions, and it is believed that the metal or metals of the group including tungsten and molybdenum, and the metal or metals of the iron group, included in the composition, function to unite the grains of carbide into a cohesive mass. As will be shown hereinafter, the resulting composition has a hardness equal to that of the compositions heretofore referred to, with a strength and resistance to deformation, especially at high temperatures, which exceeds that or said compositions.

The macro-crystalline carbides and multi-carbides, which I contemplate using in my present invention, and the method of making such car.

bides and-multi-carbides, are fully described in titled, "Carbides of tantalum and like metals and method of producing the same," to which crossreference is hereby made.

My present invention contemplates a method of producing novel hard compositions of matter from macro-crystalline tantalum carbide, macrocrystalline columbium carbide, or a macro-crystalline multi-carbide comprising either tantalum carbide or columbium carbide as a major constituent, and columbium carbide or tantalum carbide as a minor constituent. I believe that the minor constituent is present in solid solution in the major constituent, and this belief is confirmed by the X-ray spectrograms of these multi-carbides. My present invention contemplates, also, the production of new hard compositions of matter including macro-crystalline multi-carbides in which either tantalum carbide or columbium carbide constitutes the major constituent, and one or more carbides of the metals of the group including tantalum, columbium, titanium and zirconium constitute the minor constituent. A study of these multi-carbides, also, has shown that the minor constituent is present in solid solution in the major constituent within certain limiting percentages of the solute. Thus, Lcontemplate the formation of new compositions of matter from macro-crystalline multi-carbidesin which, for instance, titanium carbide or zirconium carbide, or both of them, are present in solid solution in tantalum carbide or columbium carbide, and I have found that the hard compositions of matter made from these macro-crystalline multicarbides exhibit a very useful combination of hardness, strength and resistance to deformation, surpassing to a surprising degree anything that has been produced heretofore.

In general, the percentage of carbide, or multicarbide, contained in my new composition is somewhat less than in the hard compositions of matter heretofore known, such as the two examples previously referred to, but, notwithstanding, the combined hardness, strength and resistance to deformation is greater. In general, also, in my new compositions made in accordance with this invention, the tungsten or molybdenum, or both, constitute a greater proportion of the non-carbide ingredients of the composition than has been the case heretofore, but, nevertheless, this increase in the proportion of tungsten does not result in a weakening of the composition, but, on the contrary, a strong composition is obtained and one having greater resistance to deformation, especially at high temperatures. This result is surprising, in view of the prior experience which led the worker in this art to believe that an increase in the proportion of tungsten would necessarily weaken the composition.

My invention contemplates, also, a new method of making hard compositions of matter, in which macro-crystalline carbides and multi-carbides, of the character mentioned in my pending application heretofore referred to, arecomminutcd with tungsten or molybdenum metal, and with a metal of the iron group, until the desired proportions of the ingredients are obtained, and the subsequent shaping of pieces from this powdered mixture, which pieces are then heated under a partial vacuum, as heretofore indicated. I believe that the macro-crystalline character of the carbides, or multi-carbides, used in this process contributes to the desirable results secured, in that comminution of the macro-crystalline carbides results in the production of grains thereof, having a. larger proportion of freshly fractured surface than was possible by the comminution of the amorphous materials heretofore used. I believe that this larger proportion of freshly fractured carbide surface results in a better union of the grains of carbide by the metals, as, for'instance, by the tungsten and nickel, and, hence, results in a hard composition of matter which is stronger than those heretofore made.

My invention contemplates, also,V the use of the carbides or multi-carbides in grains of differing or diverse size. I eiect this by comminuting a portion of the carbide material for a longer period than the rest and, thereafter, mixing it with the rest of the batch, and I believe that the presence of grains of carbide material of diverse size also contributes to a more effective union of the particles and results in a stronger composition. This is capable of attainment when the initial carbide is macro-crystalline.

Heretofore, it has been the practice to comminute the ingredients of the hard composition under a non-oxidizing bath. Naphtha, that is to say, a light hydrocarbon consisting principally of hexane, was customarily used for this purpose. My invention contemplates, further, a special treatment of this 'light hydrocarbon, as commercially obtained, prior to its use as the comminuting bath. I subject this light hydrocarbon to the action of a metal such as sodium, potassium, rubidium, caesium, lithium or calcium, which metal reacts with any oxygen or sulphur-containing compounds, which may be present in the light hydrocarbon as impurities, and thus removes from the bath any impurities which may tend to promote the oxidation of the material comminuted therein. This is a desirable step in the process, because it tends to prevent oxidation of the comminuted material, on the freshly fractured surfaces thereof, and, hence, eliminates any reaction of such oxidized surfaces with carbon in the subsequent heat treatment, which would tend to weaken the resulting composition and make it more brittle.

My invention contemplates, further, the heat treatment of the shaped bits or pieces under a vacuum which is substantially greater than that heretofore used, and also contemplates the beginning of the heat treatment of the shaped bits before the vapors of the hydrocarbon bath have been entirely removed therefrom. Heretofore, it has been the practice to dry the powdered mixture completely before pressing and heat treatment, so as to remove all hydrocarbon vapors therefrom. This has been done because the presence of hydrocarbon vapors contaminated the oil used in the oil pump, by which the partial vacuum was created in the heat treatment chamber, and thus prevented the obtaining of as high a .degree of vacuum as was desirable. This drying of the powdered mixture to eliminate the hydrocarbon vapors resulted in the partial oxidation of the freshly fractured surfaces of the material and that contributed to a decreased strength of the composition. I propose, therefore. to dry the powdered mixtureonly partially before pressing into shape and heat treatment, leaving about 2 per cent of hydrocarbon in the powdered mixture. I connect the heat treatment chamber with a mercury diffusion pump which has the capacity of removing the hydrocarbon vapors effectively as well as other vapors and gases, and I connect the outlet of said .mercury diffusion pump with an oil pump such as has been used heretofore. As a result, the presence of hydrocarbon vapors in the pressed bits is not objectionable, since they .are

removed by the mercury diffusion pump, and by the use of the mercury rdiffusion pump and the n oil pump I am able to obtain a higher degree of vacuum in the heat treatment chamber than has been possible heretofore'. Iy believe that this conytributesmaterially to my,l success in obtaining hard compositionsA of matter of rgreater strength,

which are produced with certainty.

They following kare specific examples of new compositions of matter, made in accordance 'with my invention, from macro-crystalline carbides f and multi-carbides of the characterdescribed in my pending application'for United States Letters Patent, Serial No. 31,521.r In the formulas, given in this specification, for these multi-carbides, I

have included in parentheses the symbol or sym bols for the metal or'metals, the carbidesof which form .the minor constituent.k It is necessary, in

forming hard compositions of ymatterr from these carbides and multi-carbides to provide other metals, which I believe perform the function of uniting the grains of carbide or multi-.carbideto form a cohesive mass and forming ay matrix in rmost circumstances, to form the sort of matrix desired.

I have foundv that a very satisfactory hard comyposition of matter mayk be formed from mac ocrystalline TaC, W and Ni, as follows: The

position, W, from 10 to 40 per cent, and Ni, from 5 to 15 per cent. The range of proportions which I prefer is TaC, from 70 to 82 per cent, W, from 11 to 38 per cent, and Ni, from 5 to 12 per cent.

. The following are the specific proportions of the ingredients in two specimens of this composition, that I have made and found useful: e

In each of these specimens, the tantalum carbide used as the starting material was macrocrystalline and had a carbon content in true monoatomic ratio to the tantalum present and, in that respect, distinguishes from the amorphous material heretofore known as tantalum carbide. The, specimens, above mentioned, were subjected to tests to determine their hardness, strength and resistance to deformation, especially at high temperatures. hardness of 89.8 and a breaking strength of 1720 kilograms, determined in the same way as with the prior compositions hereinbefore mentioned. Lathe tests showed that this composition of matter suffered less deformation, atl the high temperatures resulting from the cutting action, than the prior compositions. In other words, this new hard composition of matten'specimen A, did not show a tendency to mushroom" under conditions which would cause the prior compositions to do so. Tests upon specimen B, which, in proportion 'of ingredients, was about the same as one of the prior compositions 'referred to, didering there- In general, I have found that a -f aC may constitute from tof82 per cent of the com- Specimen A had a Rockwell Av yfrom inthat it is made from macro-crystalline tantalum carbidel insteadof amorphous material.,

showed that it had a Rockwell A hardness of f 87.62 and a breaking point of 2320 kilograms.

Comparison with the rprior compositions shows that specimen Ay was harder than the prior composition containing 78 percent amorphous tantalum carbide and not. quite so strong, having a breaking strength of 1720 kilograms, as compared with 1980 kilograms. Thisspecimen did, however, exhibit increased resistance to deformation at the cutting temperature. Specimen A Wasi about as hard as the prior composition containing 80 per cent amorphous tantalum carbide tion of strength, hardness and resistance to deformation than the prior compositions. f

'Ihe following is a vspecific example of a new l composition of matter, made in accordance with my present invention',`r usingr 7macrocrystalline CbC'as the starting material. The macro-crys- `talline CbC may constitute from 40 to -75 per cent ofthe composition, W may constitutefrom 16 to 33 percent, and Ni, from 10 to 30 per cent. Ifk Mo is substituted for W, it may constitute from 9 to 20 per cent of the composition and, in that case, Ni may constitute from 12 to 33 per cent. I prefer that, where W is used in the composition, the CbC should range from 55 to 65 per cent of the composition, W, from 18 to 22 per cent, and Ni, from 15 to 25 per cent. If, however, Mo be used in place of W, the preferred range of proportions is as follows: CbC, to 72 per cent, Mo, 10 to 14 per cent, and Ni, 18 to 27 per cent. Thespecic proportions of ingredients used in the making of a specimen of this composition from macro-crystalline CbC is as follows: CbC, 59.4 per cent', W, 20.7 per cent, and Ni, 19.9 per cent. a Rockwell A hardness of 85.2 and a breaking strength of 2030 kilograms. While not quite so hard as prior compositions made of amorphous tantalum carbide, it exceeded these compositions in strength and was far superior in strength and resistance todeformation to any materials heretofore made from amorphous columbium carbide.

The following are the specific proportions of a composition made from macro-crystalline CbC, using molybdenum in place of tungsten: CbC, 73 per cent,- Mo, 12 per cent, and Ni, 15 per cent. I believe that this composition also exhibits an excellent-combination of strength, hardness and resistance to deformation, especially at high tcmperatures.

A valuable hard composition of matter may also be made, in accordance with my present invention, using as the starting material the macrocrystalline multi-carbide, in which TaC constitutes the major constituent, and CbC the minor -constituent. This multi-carbide is expressed by the formula Ta.(Cb)A C. The CbC may constitute from 1 to 2 5 per cent of the-imultl-carblde. In this composition, the Ta(Cb)C may constitute Tests on this specimen showed that it had from 50 t'o 81 per cent of the composition, W, from 13 to 43 per cent, and Ni, from 5 to 15 per cent. 'I'he preferred range of proportions is as follows: CbC, from to 13 per cent of the Ta(Cb)C, Ta(Cb)C, 68 to 80 per cent, W, 13 to 25 per cent, and Ni, 5 to 12 per cent. The specic 'proportions of an actual specimen of this composition, made from macro-crystalline Ta(Cb C, in which the proportion of CbC was 8.8 per cent, are as follows: Ta(Cb) C, 75 per cent, W, 15 per cent, and Ni, 10 per cent. Tests upon this specimen showed that it had a Rock-A well A hardness of 88.5 and a brealn'ng strength of 2060 kilograms. Thus, in both strength and hardness, this composition was superior to the prior compositions hereinbefore mentioned. Tests upon cutting tools, including bits made from this composition, showed that they were very much better than any heretofore known, in that the tools did not fail, either by deformation, that is, mushrooming, or by chipping. Cutting tools made from this composition have been put to actual use at a governmental arsenal, in turning anti-aircraft projectiles, and this experience has demonstrated that these tools will cut longer, without chipping or showing fatigue cracks, and without the necessity of frequent dressing, than any heretofore known.

The specic examples of hard compositions of matter, made -in accordance with my invention, just given, are illustrative of the new compositions that may be made by the use, as starting materials, of the macro-crystalline carbides and multi-carbides of the character described and claimed in my pending application for United States'Letters Patent, Serial No. 31,521. It will be understood, of course, that we have not de-' scribed specifically all of the possible combinations. In general, molybdenum may be substituted for all or a part of the tungsten in any of these compositions, it being understood that, in making such substitution, the proportion of the metal used should be adjusted in the ratio of the atomic weights of tungsten and molybdenum. It will be understood, also, that cobalt maybe substituted in Whole or in part for thernickel, the proportions being adjusted in the -ratio of the atomic Weights of cobalt and nickel. Iron may also be substituted for a part of the nickel or cobalt, but the fact that iron, in nely divided form, oxidizes readily; under the conditions present in making these compositions, renders its use in substitution for all or a major proportion of the nickel undesirable.

To express the range of proportions of these compositions, I prefer to state the porportions in molecular and atomic percentages of the ingredients. I prefer that the carbide or multi-carbide shall constitute from 68.1 to 55.64 molecular per cent of the composition, that a metal or metals of the group including tungsten and molybdenum should constitute from 15.58 to 17.66 atomic per cent of the composition, and that a metal or metals of the iron group shall constitute from 20.5 to 26.7 atomic per ce'nt of the compositions. I prefer, further, that, inthe case of the multi-carbides, the minor constituent or constituents shall -constitute'less than 40 molecular per cent of the multi-carbide, as this is about the maximum which will go into vsolid solution in the major constituent. I prefer, however, to use less than the maximum amount of 'minor constituent, which would go into solid solution in the major constituent, andI have determined that it is advantageous to have the minor constituent constitute about 2 5 per cent of the multi-carbide.

I believe that, where the vcarbide is. columbium carbide, or a. multi-carbide in which CbC is the major constituent, compositions having a better combined strength, hardnessand resistance to deformation may be produced by substituting molybdenum, in whole or in part,V for the ltungsten.

The following is the preferred method, which I propose to use for the making of these new hard compositions of matter in accordance With my present invention. 'I'he macro-crystalline carbide, or multi-carbide, is ground and comminuted in a ball mill with metallic tungsten or molybdenum and nickel, cobalt or iron. Since,

nickel is most frequently used, it has been found good practice to use nickel balls in the ball mill, the body of which is also made ofnickel, or other alloy containing nickel, so that the required portion of nickel may be introduced into the powder mixture by attrition from the balls and the body of the mill. The'comminution of the carbide, or multi-carbide, and the metallic ingredients of the comp'osition is continued for the length of time required to reduce the ingredients to the desired state of flneness and until they are present in the proper proportions.

I have found it desirable, in this step of the method, that is to say, in the preparation of the -powder mixure, to comminute a portion of the carbide, or multi-carbide, for a longer time than the rest of it, the two batches being subsequently mixed thoroughly, before subjecting the powder mixture to the succeeding steps of the process. In this way, I provide the carbide, or multicarbide, in the powder mixture in grains of differing or diverse size. I have found that desirable results are obtained if about 30 per cent .of the carbide or multi-carbide used in the commaterial for from fifteen to twenty days is required to reduce it to a grain size of about 1 micron. I have found that the presence of grains of the carbide, or multi-carbide, of diverse size is advantageous, but I am not to be conned to the percentage of large particles indicated aboveor to the precise differences in grain size, as further experience may demonstrate that these are not essential.

The carbide, or multi-carbide, used as a starting material is macro-crystalline and, therefore, of a grain size exceeding 10 microns. Before subjection to heat treatment to form the hard composition. the macro-crystalline carbide, -or multi-carbide, is, by comminution, reduced to such a grain size that it is no longer macro-crystalline, but, nevertheless, the fact that a macrocrystalline carbide has been comminuted to form the powder mixture is veryimportant, because the comminution of such macro-crystalline material provides a greater area of freshly fractured difficult to dislodge the particles of hard carbide from the matrix, under conditions of use.

The comminution of the macro-crystalline carbide, or multi-carbide, together with the other metal or metals of the compositions, is Icarried out in a ,bath of naphtha, that is to say, a liquid hydrocarbon consisting principally of hexane.

This is for the purpose of preventing the oxidation of the particles of. the powder mixture during the process of comminution, and partic- 'tion is of varying strength. I have found that this is due to slight oxidation of the freshly fractured surfaces of the ingredients, notwithstanding the naphtha bath, due, probably, to impurities contained in the naphtha, in the nature of oxygen or sulphur-containing compounds. I have, therefore, subjected the naphtha to a special treatment, before using it as the commnuting bath, for the purpose of removing these impurities from the bath. I have subjected the naphtha to freshly cut surfaces of metallic sodium, as by whttling or cutting metallic sodium beneath the surface of the naphtha. This results in the formation-of bubbles of gas in the naphtha, which indicate a reaction between the sodium and oxygen-containing compounds in the naphtha, as well as sulphur-containing comf pounds thereof. At rst, the sodium discolors immediately, losing its metallic lustre, but, on continued treatment, the naphtha loses its property of discoloring the freshly cut surface of sodium, and is then suitable for use as the comminuting bath. Whatever the reaction may be,

I have found that the process of making hard compositions of matter is more sure, and the results obtained more uniform and certain, when the naphtha is subjected to this preliminary treatment before using it as the bath in which the ingredients of the powder mixture are comto the desired neness, they are removed from the bath and partially dried, so that most of the naphtha is removed therefrom. Heretofore, it has ben the practice to dry the powdered mixture completely, either in air or under a partial vacuum. This was in order to remove from the mixture the naphtha vapors, because these vapors interfered with the securing of the degree of vacuum wished for the subsequent heat treatment. It had been found that, if naphtha vapors remained in the powder, they would contaminate the oil of the oil pump used to produce a partial vacuum for heat treatment and prevent obtaining a good vacuum at this stage. 'I'his drying of the powder, to remove naphtha vapors completely, also had a tendency to promote oxidation of freshly fractured surfaces and thus rendered the strength of the resulting composition somewhat uncertain.

I have not dried the powder, after comminution, so completely as to remove all naphtha and naphtha vapors therefrom, but have left from 1 to 5 per cent of. the naphtha in the powder. This serves, to some degree, to protect the powder from oxidation prior to and during the rst stages of heat treatment, and thus contributes to the formation of a hard composition of greater strength, and especially one having a greater resistance to fatigue cracking. The comminuted powder having been dried, to the degree indicated, is pressed into bits of the shape desired. 'I'he dimensions, of course, exceed somewhat those of the bit to be ultimately formed, so as to compensate for the shrinkage which takes place in the heat treatment.

Thebits so formed are then subjected to heat treatment under a vacuum of from 40 to 7 microns of mercury pressure, in an electric furnace; being heated for about forty minutes at a temperature of from 1400 C. to 1500 C. I have found that the best results are obtained when the temperature is somewhat above 1400\C. The temperature depends somewhat upon the ratio of tungsten to tungsten andfnickel. When this ratio is 50 per cent, a temperature of about 1425 C.

is used. When greater proportions of tungsten are used, a somewhat higher temperature is required. In my new method, a somewhat higher temperature may be used, without weakening the bit, than was possible, under the old methods, in making compositions from amorphousv tantalum carbide. Although the bits are to be heated for about forty minutes at a temperature between 1400 and 1500D C., it is to be understood that the furnace is raised slowly to this temperature after the bits have been placed therein. I usually take about one hour and twenty minutes to get the furnace up to the temperature desired and, then, heat the bits at that temeprature for about forty minutes.

As stated, this heat treatment is carried ,out under a partial vacuum amounting to from 40 to 7 microns of mercury pressure. This is a higher vacuum than has been used heretofore and I believe it contributes to the good results obtained. I use a different apparatus for obtaining this vacuum, in that the electric furnace is connected with a mercury diffusion pump which draws off and absorbs gases and vapors, including the vapors coming from the hydrocarbon of the bath, which remains in the bits when they are placed in the furnace. The outlet of the mercury diffusion pump is connected to an oil pump, such as has been used heretofore in connection with the electric furnace. By the use of the mercury diffusion pump, the hydrocarbon vapors are prevented from contaminating the oil of the oil pump and, by this combination, the pressure is reduced, within the treatment chamber of the electric furnace, to a degree which has not been attained heretofore.

The drawing annexed to this specification illustrates this apparatus diagrammatically. The bit or bits I0 are placed in a graphite crucible II having a lid I2, which crucible is surrounded by a refractory lining I3 and mounted upon a refractory support I4. This is enclosed within a refractory sleeve or cylinder I5, mounted upon a water-cooled base I6 and having a water-cooled cover I`I, provided with a peep hole I8. rIhe cover II is provided with an outlet connection I9, and also with a connection 20 to a gauge which indicates the pressure within the treatment cham.- ber. The refractory cylinder I5 is surrounded by a cooled coil 2|, connected to a source ofsuitable electric current of high frequency. The outlet I9 of the treatment chamber is connected td a mercury diffusion pump, indicated diagrammatically at 22. This is a standard piece of apparatus and the Gaede mercury diffusion pump, manufactured by E, Leybolds Nachfolger A; G., of Berlin, Germany, is one which I have found suitable for this purpose. A detailed description ofthis mercury diffusion pump is not necessary. The outlet 23 of the mercury diiusion pump is connected to the inlet 24 of a suitable oil pump, indicated diagrammatically at 25, and having an outlet 26.

When the bits are placed Within the furnace,

they include a small percentage of liquid hydrocarbon from the bath, which helps to protect them against oxidation up to this stage of the process. The mercury diiusion pump and the oil pump being put in operation, the furnace is gradually evacuated and the mercury diiusion pump is eiective in removing the hydrocarbon vapors coming from the bits, without any contamination of the oil in the oil pump. By this combination of pumps, therefore, I am able, notwithstanding the presence oi" hydrocarbon in the bits, to produce a higher degree of vacuum in the furnace, and, because of this, the bits may be -treated at a somewhat higher temperature, without loss of strength. I believe that this contributes also to the good results which I have been able to obtain.

I believe that one reason for thegood characteristics of hard compositions of matter, which have as an ingredient a comminuted macrocrystalline multi-carbide including TiC or ZrC, is that, when the TiC or ZrC, or both of them, are in solid solution in the TaC or CbC, they are capable of treatment by processes of powder metallurgy, which would destroy their surfaces when present alone, in the form of the chemically simple ZrC or TiC. That is to say the TaC or CbC, in which the ZrC or TiC is dissolved, keeps it from being oxidized Vor otherwise reacted upon, during the grinding and heat treatments. Indicative of this is the fact that TiC and ZrC, per`se, cannot be prepared by the method used to produce macro-crystalline TaC, but, when prepared in solid solution in TaC or CbC, they can be treated with acid, and dried with air, and preserve an exact monatomic ratio of carbon to metal.

Another reason for the great utility of the hard compositions of matter, including a comminuted macro-crystalline multi-carbide as an ingredient, is that such multi-carbides are harder than the simple carbides, following the generalization that all solid solutionsY are harder than their simple components. This effect is fundamental and is believed to be due to the straining of the atomic lattice, which is stressed internally by the substitution of atoms of diierent atomic radius in place of the Ta. or Cb.

- Furthermore, compositions' made with macrocrystalline multi-carbides as ingredients generally have lower thermal conductivity, for the strained and harder lattices are poorer conductors. This is an advantage when the composition is used incertain kinds of drawing dies and tools, for, in these cases, a greater proportion of of the heat, generated by mechancial Work at the point of contact, is distributed to the Piece on which the work is done. This may be a factor in the successful results obtained in cutting hardened high speed steel with the composition, hereinbefore mentioned, made with comminuted Ta(CbTi) C as an ingredient. In the cutting tests of this composition, it was observed that the chips of high speed steel came off at a yellow or white heat, at which temperature this steel is soft and workable, although it is still hard at a red heat, unlike steels which .do not have this property of red-hardness. In this 'specimen of hard composition, the thermal conductivity was observed to be .036 calory per degree C., per second, per centimeter, while a similar composition made with TaC as the hard ingredient had a thermal conductivity of .06 calory, per degree C., per second, per centimeter. l

Whenever I use the term macro-crystalline" in the appended claims with reference to a carbide or multi-carbide, I mean a carbide or multicarbide having particles whichaverage greater than .01 millimeter in largest cross `section dimension and produced by the reaction between a metal or metals and carbon in the presence of a menstruum other than the metal or metals.

I am aware that the methods herein disclosed may be varied considerably, without departing from the spirit of my invention, and, therefore, I claim my invention broadly as indicated by the appended claims.

What I claim is:

1. The method of making hard compositions of matter comprising the comminution of a macrocrystalline carbide of a metal of the group consisting of tantalum and columbium, with or without, as a minor constituent, one or more of the carbides of the metals of the group consisting of tantalum, columbium, titanium and zirconium, mixing therewith a. comminuted metal of the group consisting of tungsten' and molybdenum and a comminuted metal of the iron group, forming a piece of required shape from the powder by a carbon content in monatomic ratio to the metal present, mixing therewith a comminuted metal of the group consisting of tungsten and molybdenum anda comminuted metal of the iron group, forming a piece of required shape 'from temperature exceeding 1400 C. and 'under reduced pressure.

3. The method of making hard compositions of matter comprisingv the comminution of a macrocrystalline tantalum carbide, characterized by a carbon content in'monatomic ratio to the tanta- 1um,-mixing therewith a comminuted metal of the group consisting of tungsten and molybdenum and a comminuted metal of the iron group, forming a piece of required shape from the powder mixture, and heating the piece at a temperaV ture exceeding 1400 C. and under reduced pressure.

4. The method of making hard compositions of matter comprising the comminution of a. macrocrystalline columbium carbide, characterized by a carbon content in monatomic ratio to the columbium, mixing therewith a. comminuted' metal of the group consisting of tungsten and molybdenum and a comminuted metal of the iron group, forming a piece of the required shape from the powder mixture, and heating the piece at a.

temperature exceeding-1400 C. and under reducedl pressure.

the powder mixture, and heating the piece at a 5. The method of making hard compositions of v matter comprising the comminution of a macrocrystalline multi-carbide having, as a major constitutent, a carbide of a metal of the group 5 consisting' of tantalum and columbium, and, as a minor constituent, a carbide or carbides of a metal or metals of the group consisting of tantalum, columbium, titanium and zirconium, mixing with said comminuted multi-carbide a comminuted metal of the group consisting of tungsten and molybdenum and a comminuted metal of the iron group, forming a piece of the required shape from the powder mixture, and heating the piece at a temperature exceeding 1400 C. and under reduced pressure. f

6. The method of making hard compositionsl of matter comprising the comminution of a macrocrystalline multi-carbide vwhich includes, in a single phase body, a plurality of carbides of `meta1s zirconium, mixing therewith a comminuted metal of the group consisting of tungsten and molybdenum and a vcomminuted metal of the ironv group, v

forming a piece of the required shape from the powder mixture, and heating the piece at a temperature exceeding v1400a C. and under I0 pressure.

v 8. The method of making hard compositions of matter comprising the comminution of a macrocrystalline multi-carbide, having columbium carv bide as a major constituent, and, as a minor constituent, a carbide of a metal of the group consisting of tantalum, titanium and zirconium, mixing therewith a comminuted metal of the group consisting of tungsten and molybdenum and a comminuted metal of the iron group, forming a piece of the required shape from the powder mixture, and heating the piece at a temperature exceeding 1400u C. and under reduced pressure.

9. 'I'he method of making hard compositions of matter comprising the comminution of a carbide of a metal of the group consisting of tantalum and columbium in batches for varying periods, Whereby the batches are of different particle size, mixing said batches of carbide with a comminuted metal of the group consisting of tungsten and molybdenum and a comminuted metal of the iron group, forming a piece of the required shapev from the powder mixture, and heating the piece at a temperature exceeding 1400,C. and under reduced pressure.

10. The method of making hard compositions of matter which comprises the comminution of a hard carbide and other matrix-forming metals, in a bath of liquid hydrocarbon, to prevent oxi- Yof the group consisting of tantalum, columbium,V

reduced v dation of the freshly fractured surfaces of said y materials, removing the powdered ingredients from the bath, and driving 01T the major portion of hydrocarbon therefrom, leaving, some hydrocarbon in the powder mixture to protect the same 'from oxidation during the succeeding treatment, forming a piece ofthe required shape from said powder mixture moistened with hydrocarbon of the bath, and heating said piece to a temperature exceeding 1400 C. in a chamber from which gases and vapors are withdrawn by a mercury diffusion pump.

11. The method of making hard compositions of matter comprising the comminution of a hard carbide and matrix-forming metals in a bath of liquid hydrocarbon to prevent oxidation of the freshly fractured surfaces of said ingredients, removing the powder mixture from said bath, driving off said hydrocarbon from the powder mixture until from one to five per cent thereof is left, forming a piece of the required shape from said powder, and heating the piece vto a temperature exceeding 1400 C. in a chamber from which gases andv vapors are withdrawn by a mercury diiusion pump and an roil pump connected in series.

v 12. The method of forming hard compositions however, v

of matter comprisingthe comminution of a hard v carbide and matrix-forming metals in a bath of liquid hydrocarbon, removing the mixture of powdered ingredients from said bath, forming a piece of the required shape therefrom, and heating said piece, while moistened with hydrocarbon, to a temperature exceeding 1400" C. in a chamber having a pressure of from 40 to 'l micronsofV mercury. f

v13. The-methodv of making hard compositions of matter comprising the subjection of a bath of liquid hydrocarbon to the action of a metal of the group consisting of sodium, potassium,fru-

bidium, caesium, lithium and calcium, commiv nuting a carbide of a metal of the group consisting of tantalumv and columbium, together rwith a metal of the group consisting of tungsten and v molybdenum and a metal of the iron group, in said bath of liquid hydrocarbon, drying the powder mixture thus formed, forming a piece of required shape therefrom, and heating the piece at a temperature exceeding 1400 C. and under reduced pressure.

14. The improvement in the process of powder metallurgy, which consists in subjectinga bath of liquid hydrocarbon to the action of a metal of the group consisting of sodium, potassium, rubidium, caesium, lithium and calcium, and then comminuting the materials to be subjected to powder metallurgy in said bath of liquid hydrocarbon.

15. 'Ihe improvement in the process of powder metallurgy, which consists in subjecting a bath of liquid hydrocarbon to the action of freshly cut surfaces of a metal of the group consisting of sodium, potassium, rubidium, caesium, lithium and calcium, until said freshly cut surfaces cease to. discolor, and then comminuting the ingredients to be subjected to powder metallurgy in the bath of liquid hydrocarbon so treated.

PHILIP M. MCKENNA. 

